1. Field of the Invention
This invention generally relates to a razor comb. More particularly, this invention relates to a spare razor blade unit for a razor comb. The razor blade unit of the present invention can elongate the life of its blade by facilitating alternate utilization of blade portions.
2. Prior Art
In FIG. 14 is shown a conventional spare-type hair razor blade unit 1' comprising a blade 3 and a blade holder 2. The blade 3 has two surfaces 3a and 3c and a blade edge 5. The blade holder 2 comprises two surfaces 2a and 2b connected with a backbone 2c, which is formed by bending a metal plate. The holder surface 2a has a straight edge 20a while the surface 2b has a wavy edge 20b having a plurality of parabolic protrusions 4b. The two edges 20a and 20b provide a slit therebetween for securely holding the blade 3. The blade edge 5 protrudes from the slit. The blade 3 is sandwiched between two holder surfaces 2a and 2b with the parabolic protrusions 4b for combing hair protruding beyond the blade edge 5. The parabolic protrusions 4b partially cover the blade edge 5 of the blade surface 3b while the blade edge 5 of the blade surface 3a is left uncovered, providing covered blade portions B and uncovered blade portions A for cutting hair. As can be seen in the figure, blade portions A and B appear on the blade edge 5 alternately. This razor blade unit 1' can be attached to and detached from a blade unit holder not shown in this figure.
In FIG. 15 is shown another conventional spare-type razor blade unit 1" disclosed in Japanese Patent Application No. 7-67847 filed by the present applicant, which is nearly identical with the foregoing razor blade unit 1' except that this razor blade unit 1" further comprises an elliptic window 6 provided in the holder surface 2a to receive a boss 3d fixedly provided on the blade surface 3a. The sliding of the boss 3d with a finger along the elliptic window 6 facilitates the blade 3 to slide within the blade holder 2 in the directions shown by arrows. Thus, this razor blade unit 1" facilitates alternate use of blade portions A and B. The covered blade portions B turn into uncovered blade portions A. The blade edge 5 of the razor blade unit 1" can be used theoretically twice as long as that of the razor blade unit 1'.
As will be understood by a person skilled in the art, a razor comb incorporating either razor blade unit 1' or 1" can be appropriately used only by either a right-handed person or left-handed person since the razor blade units 1' and 1" can provide adequate cutting of hair in a single direction only because the cutting performance of the blade edge 5 is subtly different between the two cutting directions. Therefore, such conventional razor blade units are utilized "reversely" between left-handers and right-hander. Additionally, a single user, left-hander or right-hander, often wishes to use a razor comb in both directions to trim hair by reversing the attachment (to the blade unit holder) of the razor blade unit. Such a reversing of the blade unit when required often is very inconvenient and impractical.